stream-start-line-p

stream-start-line-p Generic Function

Summary

A generic function that returns t if the stream is positioned at the beginning of a line.

Package

stream

Signature

stream-start-line-p stream => result

Arguments

stream⇩

A stream.

Values

result

A boolean.

Description

The generic function stream-start-line-p returns t if stream is positioned at the beginning of a line, and nil otherwise. It is permissible to define a method that always returns nil.

Note that although a value of 0 from stream-line-column also indicates the beginning of a line, there are cases where stream-start-line-p can be meaningfully implemented and stream-line-column cannot. For example, for a window using variable-width characters the column number is not very meaningful, whereas the beginning of a line has a clear meaning.

The default method for stream-start-line-p on class fundamental-character-output-stream uses stream-line-column. Therefore, if this is defined to return nil, a method should be provided for either stream-start-line-p or stream-fresh-line.